W126 heater core swap
 

Since I'm doing my evap core in the 300SEL here, I am going to go ahead and do the heater core...

Now, is there any reason to replace those aluminum hoses from the core to the monovalve?

cdplayer
 

OOOOOOOOO.....That's a job that gonna require alot of patience. I took a W126 dash apart to get a core just to have as a spare. Parts were half off at Pic N Pull then. Couldn't pass up the deal. But never had to actually
do the repair and replace.

As for the hoses, my guess is if there is no evidence of a leak, probably not. Good luck.

Nah, it's not that difficult of a job... just time consuming. People blow things out of proportion quite a bit online who have no business getting that deep into a repair.

Hell, I can do 617 oil lines in 90min start to finish with a new motor mount installed and a starter in less than two hours...

Evaporator Core
 

I just got done doing my 420 SEL where I replaced the evaporator core, expansion valve and dehydrator. It was very time consuming and as I took it apart I labeled wires and put bolts and nuts along with other goodies into lunch bags and labeled them too. This helped in putting it back together.

I did not change the heater core since these hardly go when cooling system is maintained properly. I did change all the bulbs in my instrument cluster though.

Just for future reference incase I ever have the pleasure of a failure - how difficult is it to replace the heater core in a W126? Entire dash removal like on the W140? I was thinking it was not as involved as the W140, but from what I am making of this thread it is.

Why do car companies have to make these so difficult to get to anyway?

Back in 1996, my uncle had to replace one in his wifes 1985 Ford Thunderbird and the entire dash had to come out and what was even worse on this one is that it had the digital electronic cluster.

When the HC went out on my mothers 98' Oldsmobile Achieva the book said entire dash had to come out, but the shop said he did not have to remove the entire panel to change it.

I just did one in my ex 1991 Jetta, yes the dash had to come out but it's not really that big of a deal. Just time consuming. (FWIW the reason it failed was probably green coolant)

How much is a new heater core? If its cheap you may as well do it while you have the dash out.

-Jason

The classic heater-repair madness was the early-70's Olds Cutlass. You had to remove the RIGHT FENDER to get to the heater core or fan.
Easier than a 140 dash though I would think.

DG

No doubt. I had a 1969 Chevrolet Caprice that had a new heater core installed and I found out on that car too that the RF fender had to come off to change it. NOTHING on the dash had to be touched.

in all my yrs working on benzes i have never seen a heater core leak.they are made of metal not plastic like american iron.maybe it has something to do with the weather in germany.you can always roll the windows when warm but when it gets cold you cannot survive without a heater.

They're not entirely metal, the upper and lower portions are plastic, just like a radiator....

I flushed the 300sel over the summer and rebuilt it, so far still holding six months later. :)

Not that you need to do this to change a heater core, but NEVER jack up the car by one of the front jacking points when the dashboard is out of the car.

"Why would I do that," you ask? I really don't know, but if you do the windshield will crack.

Mercedes put out a bullitin on this back in the 1980's, so I guess someone did it somewhere. Maybe they were waiting on a part and decided to change the front brakes while the car was in the garage.

Pooka

Well, I know a person at work whose father has a 1990 420SEL. They know I have a 1988 300SEL, so they normally ask me alot of questions.

I think they may have a heater core seeping because they said sometimes there is a faint smell of coolant in the car if its been driven, parked and got back into and started within a few minutes, then the smell goes away and never smelled again. He said this morning they started the car, (it was in the 40s early this AM) and placed the mode on E/C and set the fan on automatic. When the fan first came on, there was a very little bit of steam come up on the windshield, but it went away within about 5 seconds and it never came back, nor was any coolant smelled. I am wondering IF this is a possible core leak. Seems its done this for a long time now and never got any worse. If it is a core leak, it seems very minor and wondering if since it was so minor if there was some sort of product that could be put in the cooling system TEMPORARILY that would fix the leak for awhile. He said his dad does not have alot of money to spend, nor is able to do such a task, since it seems like changing the core on these are so time consuming.

Ironic, because I have heard this is uncommon on these cars, but seems like its not really.

I would not mind knowing either since I had a car like this too... never know, for future reference. If mine ever goes, I will sell the car. I would not "trust" the car again after the dash was completely removed.

Thanks for any advice I can relay.

it is probably the small heater at the bottom of the windshield[rubber hose] that has the leak.take out wiper arms and remove panel in front of windshield to gain access.not uncommon.

Oh, that would be so cool if that was the problem.... He would really be relieved. I will relay or might even check it myself for him! Thanks!